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"""
Part of the BlackStar filesystem (bsfs) module.
A copy of the license is provided with the project.
Author: Matthias Baumgartner, 2022
"""
# imports
import typing
# bsfs imports
from bsfs.utils import URI, typename
# exports
__all__: typing.Sequence[str] = (
'ClosedNamespace',
'Namespace',
)
## code ##
class Namespace():
"""A namespace consists of a common prefix that is used in a set of URIs.
Note that the prefix must include the separator between
path and fragment (typically a '#' or a '/').
"""
# namespace prefix.
prefix: URI
# fragment separator.
fsep: str
# path separator.
psep: str
def __init__(self, prefix: URI, fsep: str = '#', psep: str = '/'):
# ensure prefix type
prefix = URI(prefix)
# truncate fragment separator
while prefix.endswith(fsep):
prefix = URI(prefix[:-1])
# truncate path separator
while prefix.endswith(psep):
prefix = URI(prefix[:-1])
# store members
self.prefix = prefix
self.fsep = fsep
self.psep = psep
def __eq__(self, other: typing.Any) -> bool:
return isinstance(other, type(self)) \
and self.prefix == other.prefix \
and self.fsep == other.fsep \
and self.psep == other.psep
def __hash__(self) -> int:
return hash((type(self), self.prefix, self.fsep, self.psep))
def __str__(self) -> str:
return str(self.prefix)
def __repr__(self) -> str:
return f'{typename(self)}({self.prefix}, {self.fsep}, {self.psep})'
def __getattr__(self, fragment: str) -> URI:
"""Return prefix + fragment."""
return URI(self.prefix + self.fsep + fragment)
def __getitem__(self, fragment: str) -> URI:
"""Alias for getattr(self, fragment)."""
return self.__getattr__(fragment)
def __add__(self, value: typing.Any) -> 'Namespace':
"""Concatenate another namespace to this one."""
if not isinstance(value, str):
return NotImplemented
return Namespace(self.prefix + self.psep + value, self.fsep, self.psep)
class ClosedNamespace(Namespace):
"""Namespace that covers a restricted set of URIs."""
# set of permissible fragments.
fragments: typing.Set[str]
def __init__(self, prefix: URI, *args: str, fsep: str = '#', psep: str = '/'):
super().__init__(prefix, fsep, psep)
self.fragments = set(args)
def __eq__(self, other: typing.Any) -> bool:
return super().__eq__(other) and self.fragments == other.fragments
def __hash__(self) -> int:
return hash((type(self), self.prefix, tuple(sorted(self.fragments))))
def __getattr__(self, fragment: str) -> URI:
"""Return prefix + fragment or raise a KeyError if the fragment is not part of this namespace."""
if fragment not in self.fragments:
raise KeyError(f'{fragment} is not a valid fragment of namespace {self.prefix}')
return super().__getattr__(fragment)
## EOF ##
|
